Is my boat sitting too low in the back?

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Post Options Post Options   Likes (0) Likes(0)   Quote Sambo Black Quote  Post ReplyReply Direct Link To This Post Topic: Is my boat sitting too low in the back?
    Posted: 25 Jan 2022 at 7:33am
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Hi all and thanks in advance for all the responses.

I recently purchased a 1986 sea nymph stinger 506 which is powered by a 115hp mercury optimax.
just wondered if anyone thinks I’m sitting too low at the back?

I can’t seem to add any photos to this post ( if someone can tell me how to add photos I will) but the the water level is above the engine well drain holes at the back. It’s sits about 150mm below the lowest point on the engine well. The boat sits like this at idle and at low speeds until up on a plane and then it looks fine. I know this is part of the design of these deep engine wells but just thought it was a little off, my old boat never sat that low even loaded up with people.
there was just 2 of us on board with a battery and 40odd litres of fuel in the back.
The boat has enough seats for 6 people so would like to get that many in if I had to but unsure with how it sat with only 2.

I’m just learning with boats I know a bit but not much but I atleast know to distribute the weight as best I can so would do that if I had some fat arses on the boat.

I’m pretty sure the engine is not too big for the boat.

what do you all think?

thanks again for any response

cheers,

Sam

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Post Options Post Options   Likes (0) Likes(0)   Quote Sambo Black Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan 2022 at 7:35am
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Post Options Post Options   Likes (0) Likes(0)   Quote Sambo Black Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan 2022 at 7:36am
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Figured out how to post photos


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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan 2022 at 8:33am
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SNs generally sit higher, , even with big motors the drain holes are inch or so above water line at rest.
My 1st concern is a following sea, or if back up into a chop even a small chop.
And watch if drop off the throttle a little quick, the wake wave behind catch up and spill inside the boat.
 That is a 20" transom, is the engine 20 or 25"?

 And why is there a perma trim, 115 hp would be max power if a little over. A 115 on the back of a Commander, is bottom of well powered.
 Only time a perm trim is needed is with significantly under power boats... If changing the prop rake doesn't drop the bow, lift the stern.
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Post Options Post Options   Likes (0) Likes(0)   Quote Sambo Black Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan 2022 at 9:12am
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Thanks for your rsponse mate, really appreciate it.

I don't know much about boats but i thought it was a little odd at how low it is sitting.

Im not sure if its 20 or 25'' i will have to measure up, the boat is back in a storage lockup so i will measure this next time.



And Can you elaborate on perma trim? not sure what this is sorry.

I have only owned the boat 2 weeks so i will ring the dealer and see what they have to say. The boat was traded in and they said they hadn't driven it so they likely don't know there is a potential issue. I couldnt test drive it either because both the boat dealer and myself couldnt find a suitable time that worked for both - might have been a mistake on my part =(  


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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan 2022 at 9:59am
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Can you elaborate on perma trim?

 1st pic that plate bolted on to the cavitation plate under the water..
From factory manufactures do not put holes in the cavitation plate to fit the after market permatrims.. they do not produce or sell them, and if bolted on it voids warrentees.

 They are used  when a boat is slow to go over the bow wave and get on the plane,
And/or the boat tends to sit with the bow up in the air excessively when getting over the the bow wave
And/ or when on the plane the bow is in the air.


I don't know much about boats
 OK
This is assuming the person at the helm knows when at rest, trim right down, move throttle forward, boat then clibs over the bow wave very easy, once on the plane then trim up... Listen to the engine.. there is a point that you will hear air being sucked into the prop.. trim down slightly, goes way.. The other thing to watch is the bow bouncing too easy, called porpoising .... you trim down so you dont have ventation and just before porposing
 As your speed increase you can increase the trim
You will find at reasonable speeds, got to cross a wake.. line up about 90 deg to the wave, just before hit it, trim down.. once over trim up again..rather than adjusting throttle all the time.

Very basically, when a hull is on the plane, its about the total weight of the boat on the water, and the hp ....and enough reserve hp at any given rpm , espec in the low to high cruise rpm range, that when hit a wave/ chop, engine uses that hp to go thru without falling off the plane and/ or have to work the throttle...
Generally on 5 to 6.5m boats this result in a WoT speed in the low 40 /45mph range.
 Im would estimate with 115 on the back normal full load/ ppl etc you can hit  at least the mid 40 mph rather easy, engine right height etc.

Back to permatrim:
Under powered boat put the bow up and stern down, slow to get over bow wave etc..If min powered,  this is usually fixed by changing the rake (the angle the prop blades lean back) of the prop assuming the diam and pitch are at least ball park correct, and engine height correct.
Instead ppl do a patch fix by adding a permatrim that is a hydrofoil that lifts to the cavitaion plate, and brings the bow down. It also adds load on the power head and extra drag on the leg.

Im not sure if its 20 or 25'' i will have to measure up,

Also have a good 1m or so straight edge when go to measure...engine about 10 to 12 deg angle from the transom.. much the same as boat level, engine vertical ...
Lay the straight edge along the bottom of the hull, next to the keel, out to the motor. The cavatation plate should be ion that plane or no more than 1/2" above.

While there, look at the prop, there will be something like 13 1/2 X 19 on the hub , and a part number stamped on the prop...

Sry Smudge another long post..
But hope it explains a few things helps SB out.Wink
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Post Options Post Options   Likes (1) Likes(1)   Quote smudge Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan 2022 at 10:27am
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Steps, there's nothing at all wrong with a long post that stays on track like that one.
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Post Options Post Options   Likes (0) Likes(0)   Quote Malcolm in the Middle Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan 2022 at 11:21am
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I used to have Stinger - a great hull. Mine had 90 HP Merc 2 stroke and didn't sit as low as yours - smaller motor of course. 

Carried 6 adults at times, but only for short stints in calm water - generally 4 would be safer/more comfortable.

Re Steps' comment about power. I would consider the 90 on one of those to be minimum. They are rated to 150HP and many of them had near that as they were a popular ski boat .
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Post Options Post Options   Likes (0) Likes(0)   Quote Reel Deal Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan 2022 at 11:41am
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great post Steps!

I also use a permatrim to stop porpoising and cavitation when turn hard and sharp at speed…water skiing 
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Post Options Post Options   Likes (0) Likes(0)   Quote Sambo Black Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan 2022 at 1:25pm
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Thanks everyone for your feedback.

Steps you are very knowledgeable I’ll take those tips on board Thankyou.

There seems to be a lot of conflicting thoughts out there.
I have spoken to a few ‘boat experts’ over the phone and more are saying that it’s normal and it’s just the way the hull was designed. Still a little concerned to put any more than 4 people on. Of course if I did it would be in calm waters just to
Get to a destination.

I don’t intend on using the boat at sea, will be mainly used on lake Taupo for fishing and skiing.

I have also seen these hulls with 150hp on them hence why I didn’t think the engine was too big.


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Post Options Post Options   Likes (0) Likes(0)   Quote Bounty Hunter Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan 2022 at 7:59pm
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Originally posted by Steps Steps wrote:

SNs generally sit higher, , even with big motors the drain holes are inch or so above water line at rest.
My 1st concern is a following sea, or if back up into a chop even a small chop.
And watch if drop off the throttle a little quick, the wake wave behind catch up and spill inside the boat.
 That is a 20" transom, is the engine 20 or 25"?

 And why is there a perma trim, 115 hp would be max power if a little over. A 115 on the back of a Commander, is bottom of well powered.
 Only time a perm trim is needed is with significantly under power boats... If changing the prop rake doesn't drop the bow, lift the stern.

Hustler 570's are the Stingers closest relative - and sit low in the bum just like this

we had yamaha and johnson v6 2strokes on the back of Hustlers and the draining well holes were below the waterline at rest

i think the situation with the OP is fine - its just a combination of the deep-v nature of the hull and the transom being designed for the shorter engine legs that were the norm 30years ago

As you say - one needs to be aware of the risk of pointing the back of the boat toward the sea and possible boarding waves over the back

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Post Options Post Options   Likes (0) Likes(0)   Quote Sambo Black Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan 2022 at 8:12pm
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Thanks for your comment bounty hunter.
I had another boating guru say the same thing about the hustler.

I will be sure to be cautious with backing into waves, as I said earlier the boat will be mainly used in lake Taupo and it’s going to be a family boat so I won’t be taking them out in rough weather anyway just wanted to be sure.

Thanks for easing my mind everyone, appreciate your time and knowledge
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Post Options Post Options   Likes (0) Likes(0)   Quote Bounty Hunter Quote  Post ReplyReply Direct Link To This Post Posted: 25 Jan 2022 at 8:54pm
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take care with Lake Taupo - i think many people think it's 'just a lake' - and that there's inherently less risk than 'at sea'

but when the wind comes up - and it can often mid-morning quite quickly - a short-steep sea builds very quickly and people can be caught out with its 'un-pleasantness'

err on the side of caution until you are familiar with the lakes nature
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Post Options Post Options   Likes (0) Likes(0)   Quote Sambo Black Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jan 2022 at 4:58am
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Thanks bounty hunter.

I spent my whole childhood life boating on Taupō so know what you mean about how fast things can change out there, have got out of a few sticky situations.

Cheers
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Post Options Post Options   Likes (1) Likes(1)   Quote Dagwood Quote  Post ReplyReply Direct Link To This Post Posted: 26 Jan 2022 at 8:21am
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Might pay to bear in mind that when doing comparisons, your boat will sit lower in fresh water compared to salt. 

Maybe not by a huge amount but could be noticeable...
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Post Options Post Options   Likes (0) Likes(0)   Quote Sambo Black Quote  Post ReplyReply Direct Link To This Post Posted: 08 Feb 2022 at 7:06am
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Hi again all.

I am considering shifting my battery and spare tote tanks up the bow of the boat to combat my low sitting arse.

Someone even told me to put sandbags up there to see how it helps.


I have an auxiliary on aswell which I could remove but that would be a last straw and id prefer not to.

Just wondering what you all think?

Still feeling un-easy about how low the boat sits.

Been back to the dealer and they said it’s completely normal for this hull to sit like that…?
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Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 08 Feb 2022 at 9:06am
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Still feeling un-easy about how low the boat sits.

 yep so do I. normal or not..being aware of following seas and/ or sudden stops with wake wave coming over the back, and over the back of the engine well.
 I sit lower than would like but have the higher back to the engine well.

I have an auxiliary on aswell which I could remove but that would be a last straw and id prefer not to.

 I know lot lake and ex lake boats have auxillarys. My understanding is they cant troll slow enough on the main engine...????
Im well out of my depth and experience here for displacement hull trolling (thu know the maths)

Guys troll in salt water, kings to bill fish, main engine.
May require a compromise prop between the ideal to get out to the grounds, and trolling (semi displacement/ displacement hull) speed.

Do you actually need the Aux?
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Post Options Post Options   Likes (0) Likes(0)   Quote Sambo Black Quote  Post ReplyReply Direct Link To This Post Posted: 08 Feb 2022 at 9:14am
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Hello again steps.

I agree normal or not the need to be aware is great. Hence why I’ve been looking for advice from all who has it.

That’s correct mate, usually the main motor won’t go slow enough so the auxiliary is used to troll at slow speeds. Some one on another forum told me that I could probably troll with my main motor being the optimax 115 ? so I will look into that.

I have full confidence in my main motor the auxiliary is really only there for trolling and for a back up if something did hair to the main but aux will be off the boat half the time for skiing anyways so I could potentially do away with it.
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Post Options Post Options   Likes (0) Likes(0)   Quote Kandrew Quote  Post ReplyReply Direct Link To This Post Posted: 08 Feb 2022 at 3:18pm
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SAM, looking at the photos it does look like it is sitting way too low in the water, a lot of the 506 came out with 120hp and 140hp VROs on the back which are a lot heavier then the opti and most of them sat down on their chime line or upto 30mm below.

It does look like there’s a lot of weight on the transum. It could have water in the bottom of the hull. What I suggest first is take the whole boat and trailer down to the local weight station and weight it, once you know that then you can start subtracting the tailer weight, motor, totes and what ever was in the boat when you weighed it to get us back to the boat weight so we can see if it’s on or over weight and by how much.

Bit of a guess I would expect the whole boat, tailer and all to come in around 1200kg
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Post Options Post Options   Likes (0) Likes(0)   Quote Malcolm in the Middle Quote  Post ReplyReply Direct Link To This Post Posted: 08 Feb 2022 at 3:54pm
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Do you have tote tanks or under floor fuel? 

 In my Stinger I had the battery moved up under the drivers seat - in part for weight distribution but in part to move it away from the lowest point in the boat - which is where they are amounted as standard. 
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